1. Field of the Invention
This invention involves novel anhydride-functional polymerizable monomers and polymers and reactive compositions prepared from those monomers. The anhydride-functional monomers have the structure: ##STR2## wherein R is hydrogen or methyl.
This invention also relates to anhydride-functional polymers having an average of at least two anhydride groups per molecule and which are obtained by polymerizing, under free radical addition polymerization conditions, (i) the anhydride-functional monomer of this invention; and (ii) optionally, at least one other unsaturated monomer copolymerizable with the anhydride-functional monomer.
This invention also relates to novel reactive compositions which utilize the anhydride-functional polymer. The polymers are useful as corrosion or scale inhibitors, thickeners, dispersants and as reactive agents and/or crosslinking agents for compounds having functional groups, such as epoxy, hydroxyl or amine groups, which are reactive with anhydride groups. The anhydride-functional polymers can, therefore, be utilized in a variety of materials such as plastics, fibers, adhesives, paper sizing, inks and, particularly, coating compositions. The reactive compositions can be reacted at room temperature or force dried at temperatures ranging up to about 350.degree. F. or higher if desired. When utilized as reactive crosslinking agents for coatings, the anhydride-functional polymers may be utilized in a variety of coating applications, including primers and topcoats as well as clearcoats and/or basecoats in clearcoat/basecoat compositions. The monomers themselves can be utilized as crosslinkers, neutralizers, scale preventatives, thickeners and many other applications.
The coatings typically involve the combination of the anhydride-functional polymer with materials reactive with anhydrides such as polyepoxides, polyamines, polyols, etc. One preferred curable coating combination comprises the anhydride-functional polymer and a polyol, preferably a hydroxy-functional polymer, optionally in combination with an epoxide or polyepoxide. Another preferred curable coating combination comprises the anhydride-functional polymer, an acid-functional compound, an epoxide or polyepoxide, and, optionally, a polyol. All of these combinations provide fast reacting, durable coatings which minimize the toxicity problems which may be associated with other low temperature curing systems.
2. Description of the Prior Art
Unsaturated anhydrides, such as maleic anhydride, and copolymers made from maleic anhydride are known in the art. Such anhydride copolymers are heterogeneous with respect to the distribution of anhydride groups along the backbone of the polymer due to the abnormal copolymerization behavior of maleic anhydride with other monomers, and the acid groups generated from opening these anhydrides by reaction with hydroxyl or amine groups are not highly reactive for further cure reactions, e.g. with epoxy groups, due to steric hindrance arising from the proximity of the anhydride ring to the polymer backbone. Such anhydride-functional polymers are also relatively viscous and are difficult to utilize in combination with low levels of solvent. Additionally, such polymers may form dark colored materials when certain base catalysts, such as N-methyl imidazole, are used to accelerate a subsequent reaction of the polyanhydride with reactive materials such as hydroxy-functional compounds.
Coating compositions comprising polyanhydrides and hydroxy-functional compounds are known in the art. For example, U.S. Pat. No. 4,946,744 teaches clearcoat/basecoat combinations involving (i) a polyanhydride, for example, such as that prepared by copolymerization of maleic anhydride with (meth)acrylic monomers, and (ii) a polyol. U.S. Pat. No. 4,871,806 teaches curable compositions comprising a polyanhydride, a polyacid, a polyol and an epoxy-functional compound. U.S. Pat. No. 4,374,235 teaches anhydride-functional polymers prepared by the polymerization of an alkenyl succinic anhydride and a vinyl monomer. The prior art has not, however, taught polymers obtained by the polymerization of the novel anhydride monomers of this invention.